Prior to the development of knotless designs, bone anchor deployment instruments typically utilized anchors which had suture material either preloaded or incorporated eyelets through which a length of suture may be loaded prior to anchor introduction into the bone. The sequence of operation for deploying the anchors generally entailed passing one or more suture lengths through the soft tissue to be secured and then approximating the soft tissue to the underlying bone by tying one or more knots.
Even with the advent of knotless bone anchor designs, the ability to accurately and reliably apply tension to the sutures to approximate soft tissues to bone created additional problems. Because of the nature of knotless anchor designs, sutures are typically placed through the soft tissue to be secured before coupling them with the anchor. This required the inclusion of additional mechanisms for threading the anchors and tensioning the sutures.
Developments in constructs for approximating and securing soft tissue to bone, notably in the area of rotator cuff repair, have created the need to be able to independently secure, thread, and tension one or more of the suture strands passing through one or more bone anchors. This is typically apparent in the formation of crossed suture configurations, e.g., criss-cross type constructs, where suture limbs from two different medially placed anchors are loaded into a laterally placed anchor. Because the suture limbs may originate from different orientations or bone anchors, they may not have the same lengths and may thus need to be tensioned independently of one another.
Additionally, in certain of the bone anchor insertion instrument configurations described above, there exists a need to secure suture limbs after they have been loaded into a threading or snaring device to prevent the separate suture limbs from dropping out of the insertion device. As the sutures are withdrawn over a distance through the anchor and into the inserter, the potential for the sutures pulling out of the snare and the insertion device is significant.
Accordingly, devices and methods which allow for the tensioning of separate suture lengths independently of one another are desired. In particular, mechanisms to individually capture suture lengths and convey them to tensioning mechanisms, e.g., ratchet wheels, which are controllable to enable a user to selectively tension either or both individual suture lengths are desired. Further, a suture threading and snaring device that allows for single step loading and securing of independent suture limbs into knotless bone anchors is also desired. In particular, mechanisms that allow for the individual snaring and securing of suture limbs in conjunction with the use of a bone anchor insertion device with independent tensioning mechanisms, and that convey the independent suture limbs to the separate tensioning mechanisms, e.g., ratchet wheels, are also needed